A laser galvanometer is a specialized motion device used in the field of laser processing. It relies on two galvanometer mirrors to reflect the laser, forming movement in the XY plane. Unlike general motors, laser galvanometers have very small inertia and very light loads during movement, consisting only of two small mirrors, X and Y, each controlled by different motors. This results in a very fast system response.
The laser galvanometer operates in two basic modes: jump movement and marking movement.
Jump Movement: During jump movement, the axis moves to the position to be processed while the laser is off, so it does not affect the processing trajectory. This allows for very high-speed movement.
Marking Movement: During marking movement, the laser is on, processing the trajectory. Users need to set an appropriate movement speed based on actual processing requirements.
A galvanometer is an excellent vector scanning device. It is a special type of oscillating motor (laser galvanometer). The basic principle is that a current-carrying coil generates torque in a magnetic field. Unlike a rotating motor, the rotor has a restoring torque applied through mechanical springs or electronic methods, proportional to the angle by which the rotor deviates from its equilibrium position. When a certain current flows through the coil, causing the rotor to deflect to a certain angle, the electromagnetic torque equals the restoring torque. Therefore, it cannot rotate like a regular motor but can only deflect, with the deflection angle proportional to the current.
Basic Structure of a Galvanometer Control System
The galvanometer system consists of several parts forming a basic system. The main components of the galvanometer head are the X/Y mirrors and two motors that control the rotation of the X/Y mirrors. Depending on actual needs, a human-machine interface, encoders, etc., can be added.
Basic Requirements for the Controller
Since a laser marking machine relies on the deflection of the X/Y galvanometers to reflect the laser onto the worktable for precise engraving, the control of the galvanometers is open-loop. Therefore, it must be linear, meaning the input signal and the deflection angle must have a linear relationship. As the galvanometer is a fast and precise mechanical device, the transition from one working state to another requires the highest possible acceleration to minimize idle time during marking.
The galvanometer movement adopts a buffer zone movement method. Users need to transfer movement and process data to the axis movement buffer zone and then start the buffer zone movement. The motion controller will sequentially execute the user-transferred movement data until all movement data is completed. In the laser galvanometer motion control system, there is not only motion control but also laser control. Effectively coordinating the galvanometer movement and laser switching is crucial. Only by effectively coordinating the laser and movement can precise trajectories be achieved.
Motion Control: During marking movement, the laser moves along the given marking trajectory at the set marking speed. When executing marking-related commands, the laser galvanometer motion controller will automatically turn on the laser. If the next command is still a marking command, the laser remains on until the last marking command ends or the buffer zone commands are completed. If a jump command is encountered in the buffer zone, the laser automatically turns off until a marking command is encountered again. Before starting the movement, the galvanometer coordinates need to be adjusted to ensure the correct marking trajectory, and the buffer zone should be cleared.
Laser Control: This mainly includes controlling the laser’s on/off state and the duration of the laser emission. The laser’s on/off is controlled using OP commands. The laser energy can be controlled according to the type of laser, corresponding to the analog output, digital output, or the duty cycle of the PWM output.
Main Applications
The primary applications include laser marking, laser cutting, stage lighting control, and laser drilling. It is a non-contact, pollution-free, and wear-free new marking process, with greatly improved reliability through automated control. Laser marking uses a high-energy-density laser beam that moves in a regular pattern on the material surface while controlling the laser beam’s on/off state, causing physical or chemical changes on the target material’s surface. The laser beam can then process a specified pattern on the material surface.
Compared to traditional marking processes, laser marking has the following advantages:
Fast marking speed and clear text.
Non-contact processing, minimal pollution, and no wear.
Convenient operation and strong anti-counterfeiting capability.
High-speed automatic operation, low production cost, and reliable operation.
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